This invention relates to a sensor and control system for actuating the exhaust fan of a ventilation system. In particular, the invention relates to a sensor and control system for actuating the exhaust fan of an integrated toilet exhaust system.
Many toilet exhaust systems have been proposed. Some are retrofit systems and some are xe2x80x9cintegratedxe2x80x9d systems, i.e., substantially formed as part of the toilet during manufacture. An example of the integrated type of toilet exhaust system is described in U.S. Pat. No. 6,019,862.
Some of these systems use manual exhaust fan actuation means, such as a wall switch.
Some systems use pressure plate type switches located between the upper rim of the toilet and the toilet seat which complete the circuit to the exhaust fan upon someone sitting on the toilet seat and open the circuit when the person gets off the seat. This is the type of activation means disclosed in U.S. Pat. No. 6,019,862, which refers to U.S. Pat. No. 5,253,371 for a more complete description.
The manual actuation means suffers from the problem of people forgetting to turn the switch on at the time they sit down on the toilet or forgetting to turn it off after completing their use of the toilet.
The pressure plate type actuation means is at least automatic, but suffers from soiling and frequent breakdown.
It is an object of the present invention to provide automatic means for actuating a toilet exhaust system.
It is a further object of the present invention to provide a toilet exhaust actuation means that has no moving parts, which eliminates or reduces maintenance problems.
It is a still further object of the present invention to provide a toilet exhaust actuation means that senses the presence of a person before that person commences use of the toilet to actuate the toilet exhaust system and senses the absence of that person after toilet use is finished to deactivate the toilet exhaust system after an appropriate period of time has passed.
These and other objects are achieved by the device of the present invention. The device includes a sensing electrode located adjacent the toilet bowl which is charged to a fixed potential and exhibits an increase in capacitance in response to the presence of a person in close proximity to the toilet. A charge transfer circuit detects and measures the change in capacitance. When the required detection criteria are met a micro-controller in the charge transfer circuit generates a signal to a switch to close the circuit between a power source and the exhaust fan motor of the toilet exhaust system. During the time no signal is being sent to the switch by the micro-controller, the switch opens the circuit between the power source and the exhaust fan motor.